1. Field of the Invention
The invention relates to a tool for seaming machines.
2. Prior Art
Such a tool comprises of a central seaming chuck which engages the can end by contacting its chuck wall and pushing said can end into the can opening with its seaming chuck lip when lifting the supporting means carrying the upright standing can, and presses the flared flange of the can end against the flared flange of the can in a direction opposite to the resilience effective at said supporting means, maintaining said can end in a predetermined position with respect to the seaming rollers, thus allowing to radially adjust said rollers without impediment until their groove is able to engage said flared flanges lying one upon the other and to deform them in the desired manner. Can seaming machines for cans rotating during the seaming procedure are usually not provided with a stripping means above said seaming chuck lip. In these cases, said seaming rollers have stripping function. For this purpose, the diameter of said rollers above said profiled groove must be markedly larger than the diameter below said profiled groove and must overlap said seaming chuck lip in radial direction when the rollers are adjusted. For this purpose, a corresponding undercut is provided on the upper side of said seaming chuck in which undercut said roller section of larger diameter is received ("drives in") when adjusting the rollers.
The shape of said seaming chuck lip is substantially defined by said undercut and by a center recess on the lower surface of said seaming chuck, which recess is determined for receiving a tear-off means of tear-off can ends. Thus, the cross section of the transition area between lip and center section of said seaming chuck becomes relatively small with the risk of fissures or even breaks at said transition area due to strong alternating stresses. The risk increases with increasing chuck wall height of said can end and increasing height of said seaming chuck lip.
The center section of said seaming chuck could be enlarged to strengthen said transition area, but then, the stripping function of the seaming rollers is lost. If during a seaming procedure no can end was supplied to the can to be closed next, the seaming chuck is not able to press the can down against the resilience of said supporting means, when lifting said supporting means. Thus, the flared flange of the can is positioned considerably higher with respect to said seaming chuck lip and said seaming rollers. When (laterally) adjusting said seaming rollers, there is a risk that the flared flange of the can is rolled over the shoulder of the seaming chuck which shoulder being formed by the undercut; consequently, the can cannot be stripped and the machine has to be stopped.